I resisted the balaclava for a long time thinking it would be too hot (and it is too hot for me for temps above 20F or so). I also didnt want to ride around looking like a terrorist/bank robber. I finally bought one after freezing my face on a commute when it dropped below 25 around here. I had tried a scarf, my neck and chest were sweating, my face was freezing. I got a very thin wool balaclava and it did an amazing job wicking sweat, insulating, and regulating body heat. For me, around 25 is where I found the need to break it out. Different people will have a different threshold.

Its guaranteed to really mess up you hair beyond repair though. I got to work, re-wet my hair and couldnt make it do anything - it was going all different directions. Oh well, it was a small price to pay.